Voltra12-3-30 and weighted vest walking: what the studies show
12-3-30 means walking on a treadmill at a 12% incline and 3 mph, about 4.8 km/h (calculated), for 30 minutes [1]. In a small 2025 lab study, 14 young adults did it once and, on another day, ran until they had burned the same calories: 12-3-30 drew more of its energy from fat, about 41% against 33%, but took about 6 minutes longer, and the study didn't track weight or fat loss [1]. Weighted vests can make walking harder [2], but in a 5-week trial a heavy vest didn't change body weight [4], and in a 12-month trial a vest didn't prevent hip bone loss [5].
What 12-3-30 is
Set the treadmill to a 12% incline and 3 mph (1.34 m/s, about 4.8 km/h, calculated) and walk for 30 minutes [1]. The workout spread on YouTube and TikTok with claims that it burns fat and calories; the authors of the study below write that they knew of no peer-reviewed research testing those claims [1].
The study: one session of each
Researchers at the University of Nevada, Las Vegas enrolled 16 regularly active adults, 7 women and 9 men, with an average age of about 25 [1]. Each did one 12-3-30 session and, within seven days, one run on a flat treadmill at a pace they chose, stopping when they had burned as many calories as on 12-3-30 [1]. They hadn't eaten for at least three hours beforehand and weren't allowed to hold the handrails [1]. One woman couldn't finish the 12-3-30 session and another couldn't schedule her run, so the results cover 14 people [1].
| Measure | 12-3-30 | Self-paced run |
|---|---|---|
| Time (minutes) | 30.1 | 23.9 |
| Calories (kcal) | 308 | 310 |
| kcal a minute | 10.2 | 13.1 |
| Energy from fat | 40.6% | 33.1% |
| Energy from carbohydrate | 60.0% | 67.5% |
Averages for the 14, from Table 1 of the paper [1]. The calorie totals were matched by design, and the difference between them was not significant [1].
So 12-3-30 drew a bigger share of its energy from fat: 7.43 percentage points more than the run [1]. In calories, that's roughly 125 kcal from fat against 103 kcal, a gap of about 22 kcal (calculated from the averages, so approximate). The run burned the same total about 6 minutes faster [1].
A slip in the paper: its discussion says fat use was 7.48% lower on 12-3-30. Its own Tables 1 and 2 show the opposite, 7.43 points higher; 7.48 is the difference for carbohydrate [1].
The authors point out that what mainly drives weight loss is burning more energy overall, to reach a calorie deficit, rather than the share of that energy that comes from fat [1].
What the study doesn't show
- Anything long term. It measured one session of each. Nobody's weight, body fat or fitness was followed over time; the authors say the design can't show long-term effects, and call for randomised trials that track changes such as body composition [1].
- Results for everyone. It was a small convenience sample of mostly university-age, recreationally active adults, which the authors say limits how far the findings apply [1].
- A comparison with flat walking. 12-3-30 was compared with running, not with walking on the flat [1].
Weighted vests: how much harder is walking?
In a 2006 lab study, 10 young adults walked on a treadmill at five speeds wearing vests of 0, 10, 15 and 20% of their body weight. The vests raised the oxygen cost of walking and the load on the skeleton; effort relative to each person's capacity rose at the faster speeds but not the slower ones [2]. The abstract doesn't say by how much [2].
In a 2022 study, 20 adults walked with and without the standard CrossFit vest, 9.07 kg for men and 6.35 kg for women. It made walking harder only at a 10% incline, not on the flat or at 5% [3].
Wearing one for weeks or months
- Fat, not weight: 5 weeks. In a Swedish trial, adults with obesity (a BMI of 30 to 35) wore a heavy vest, 11% of body weight (28 people), or a light one, 1% (30 people), for 8 hours a day. Compared with the light vest, the heavy one reduced fat mass by 2.60% and raised lean mass by 1.40%, with no significant change in body weight. The heavy-vest group also spent more time sedentary, and the energy they burned and ate didn't change [4]. The trial wasn't blinded: people could feel which vest they had [4].
- Bone during weight loss: 12 months. In the INVEST trial, 150 adults with obesity, average age 66, dieted with a target of losing 10% of their weight, and all three groups lost between 9.0% and 11.2%. One group also wore a vest that put back most of the weight they lost (78% on average), asked to wear it 8 hours a day and reporting about 7; another did supervised resistance training three times a week. Hip bone density fell in all three groups, by 1.2% to 1.9%, and neither the vest nor the resistance training prevented it [5]. The US National Institute on Aging funded the trial, and Jason Pharmaceuticals, a Medifast subsidiary, donated the meal replacements [5].
- A tiny older study. In 2000, 9 women past menopause who kept up vest-and-jumping exercise for 5 years held on to their hip bone density better than 9 women from the original control group, who weren't in the programme [6]. They were volunteers who chose to carry on after an earlier study, so who took part was self-selected, and the exercise included jumping [6].
- The 2026 review. Pooling nine randomised trials with 368 middle-aged and older adults, it found that vest-plus-exercise programmes improved bone density at the top of the thigh bone and the lower spine compared with usual activity, a comparison that can't separate the vest from the exercise. Adding a vest to exercise gave a little extra fat loss, 0.73 kg on average, but no significant bone benefit over exercise alone, and that bone finding comes from a single study [7].
What isn't shown
None of these studies shows that walking in a weighted vest makes healthy adults lose weight or build bone. In the two longer trials, people wore the vest through the day rather than for walking workouts [4] [5]. Where the vest itself made a difference, it was to body fat: 2.60% less fat mass than with a light vest after five weeks [4], and 0.73 kg of extra fat loss when added to exercise [7]. None of them showed the vest itself lowering body weight or improving bone [4] [5] [7]. For 12-3-30, no one's weight or body fat was followed over time [1].
In the heat
In a Gulf summer, the WHO advises against going out and doing strenuous activity at the hottest time of day [8]. 12-3-30 is a treadmill workout, so it can be done indoors; keep outdoor vest walks to the cooler hours. Our guide to exercising in the heat covers heat illness and what to drink.
In Voltra
In the Train tab, the Cardio page has Log a session: pick Walking and enter the time, distance and calories. If you leave calories out, Voltra estimates them from a default rate for the activity, 4.5 kcal a minute for walking, set for an 80 kg person at a moderate pace. That rate doesn't account for incline or a vest, so typing in the treadmill's figure is closer. For 30 minutes of 12-3-30, the default gives 135 kcal; the study measured about 308 kcal on average, in people who averaged 75 kg [1], so the default comes to less than half (calculated).
Frequently asked
Does 12-3-30 burn more fat than running?
In one lab session, more of the energy came from fat, about 41% against 33%, but the calories were matched and the run took about 6 minutes less. The study didn't measure fat loss over time.
How many calories does 12-3-30 burn?
In the study, about 308 kcal in 30 minutes on average, or about 10 kcal a minute: 254 kcal for the women and 337 kcal for the men. The people in it averaged 75 kg.
Does walking with a weighted vest help you lose weight?
That hasn't been shown. In a 5-week trial, a heavy vest worn 8 hours a day reduced fat mass by 2.60% more than a light one but didn't change body weight. A 2026 review found that adding a vest to exercise gave about 0.73 kg of extra fat loss.
Is a weighted vest good for your bones?
The trials don't show it. In a 12-month trial of 150 older adults losing weight, a vest worn about 7 hours a day didn't prevent hip bone loss. A 2026 review found no extra bone benefit from adding a vest to exercise, though that rests on one study.
Sources
- Wong MWH, Davis DW, Perez OR, Weyers B, Green DM, Garcia AV, Navalta JW (2025). An exploratory study comparing the metabolic responses between the 12-3-30 treadmill workout and self-paced treadmill running. Int J Exerc Sci 18(6):56–64. Full text, published 1 January 2025. Tables 1 to 3.
- Puthoff ML, Darter BJ, Nielsen DH, Yack HJ (2006). The effect of weighted vest walking on metabolic responses and ground reaction forces. Med Sci Sports Exerc 38(4):746–52. Abstract.
- Gaffney CJ, Cunnington J, Rattley K, Wrench E, Dyche C, Bampouras TM (2022). Weighted vests in CrossFit increase physiological stress during walking and running without changes in spatiotemporal gait parameters. Ergonomics 65(1):147–158. Abstract.
- Bellman J, Westerterp K, Wouters L, et al. (2025). Increased weight-load improves body composition by reducing fat mass and waist circumference, and by increasing lean mass in participants with obesity: a single-centre randomised controlled trial. BMC Med 23(1):317. Full text.
- Beavers KM, Lynch SD, Fanning J, et al. (2025). Weighted vest use or resistance exercise to offset weight loss-associated bone loss in older adults: a randomized clinical trial. JAMA Netw Open 8(6):e2516772. Full text. No conflicts of interest reported.
- Snow CM, Shaw JM, Winters KM, Witzke KA (2000). Long-term exercise using weighted vests prevents hip bone loss in postmenopausal women. J Gerontol A Biol Sci Med Sci 55(9):M489–91. Abstract.
- Wang X, Zhou L, Shi T, et al. (2026). Effects of weighted vest on bone health and body fat in middle-aged and older adults: a systematic review and meta-analysis. Osteoporos Int. Abstract. Published online 14 August 2026.
- World Health Organization (2026). Heat and health (fact sheet). Fact sheet dated 31 July 2026.
Sources checked on 30 September 2026.
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